This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-235008, filed Aug. 23, 1999; and No. 2000-246319, filed Aug. 15, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an electronic exchange and a key telephone system.
An electronic exchange has been capable of controlling call reception from and call transmission to other electronic exchanges by employing the QSIG protocol defined by the European Computer Manufacturers Association, which is the international standard for digital lines.
The services can be provided by constructing the networking by use of this kind of electronic exchanges as if one single electronic exchange were operated for the user using the electronic exchanges.
FIG. 1 is a view showing a networking using conventional electronic exchanges. FIG. 2 is a view showing a sequence of a message signal forwarded between the electronic exchanges in the networking of FIG. 1.
In FIG. 1 electronic exchanges 10, 11 and 12 are respectively connected to one another in digital lines 21, 22 and 23 employing the QSIG protocol.
It is assumed now that telephones 1 and 2 communicate with one another via the electronic exchanges 10 and 11, and the telephone 2 forwards the call with the telephone 1 to a telephone 3 connected to the electronic exchange 12 so that the telephones 1 and 3 communicate with one another.
When the user of the telephone 2 executes hooking operation to the electronic exchange 11, a dial tone signal is transmitted from the electronic exchange 11 to the telephone 2. At the same time, the telephone 1 of the communication partner is made to be in the on-hold state by the electronic exchange 11.
The user of the telephone 2 dials a telephone number of the telephone 3 as the forwarding destination by the telephone 2 after having confirmed the dial tone.
The electronic exchange 11 transmits a forward acknowledgement signal xe2x80x9cFacility messagexe2x80x9d defined by the QSIG protocol to a digital line 22, in response to the dialing. At this time, specific information about the telephone number of the call destination, a person who forwards this message, a person who receives the forwarded message, etc., i.e. facility information elements are added to the Facility message.
Receiving the xe2x80x9cFacility messagexe2x80x9d from the electronic exchange 11, the electronic exchange 12 checks whether the telephone 3 is idle or not. If the telephone 3 is idle, the electronic exchange 12 transmits to the electronic exchange 11 a xe2x80x9cCall proceeding messagexe2x80x9d, which indicates that the forwarding is acceptable.
On the other hand, the telephone 2 is in the on-hook state and remains idle after the dialing.
Receiving the xe2x80x9cCall proceeding messagexe2x80x9d from the electronic exchange 12, the electronic exchange 11 recognizes that the telephone 3, which is a destination of a call to be forwarded to the electronic exchange 10, is idle and can accept the call. At this time, the electronic exchange 11 inserts the information about the forwarding into the xe2x80x9cFacility messagexe2x80x9d and transmits the message to the electronic exchange 10 so that the electronic exchange transmits a calling request xe2x80x9cSetup messagexe2x80x9d as a formal call start request to the electronic exchange 12.
The electronic exchange 10 transmits the xe2x80x9cSetup messagexe2x80x9d to the electronic exchange 12 in accordance with the information included in the xe2x80x9cFacility messagexe2x80x9d.
Receiving the xe2x80x9cSetup messagexe2x80x9d, the electronic exchange 12 checks again whether the telephone 3 is idle or not. If the telephone 3 is idle, the electronic exchange 12 transmits the xe2x80x9cCall proceeding messagexe2x80x9d, which represents the acknowledgement of acceptance for the call, to the electronic exchange 10. At the same time, the electronic exchange 12 transmits a calling signal to the telephone 3 and transmits xe2x80x9cAlertingxe2x80x9d, which represents a state of extension calling, to electronic exchange 10.
Incidentally, with the conventional electric exchanges, in a case where a calling operation is executed at the telephone 3 or a call from the other telephones is received at the telephone 3 after the electronic exchange 12 has received the xe2x80x9cFacility messagexe2x80x9d and transmitted the xe2x80x9cCall proceeding messagexe2x80x9d representing that the forwarding is acceptable, when there is an incoming call from the electronic exchange 10, the telephone 3 is busy and thus the forwarding is not accomplished, as shown in a flow chart of FIG. 3. In this case, there is also a drawback that the data traffic unnecessarily increases since an invalid signal is transmitted within the network.
Calling restriction as to whether a call from extension telephones should be accepted is often executed in accordance with international, longdistance and local destinations of calling. In this case, with the conventional electronic exchanges, the information unique to the manufacturer, common to only electronic exchanges of the same manufacturer is inserted into the manufacturer information element of the QSIG protocol, and is provided to electronic exchanges connected to the public telephone network by those connected to extension telephones.
Transmission of the manufacturer information element needs to be executed under the dedicated coding rules, and software for transmission and reception is also required. For this reason, the load on the CPU (central processing unit) in the electronic exchange may increase, technical problems may arise, and circuitry may be complicated due to the addition of new hardware.
FIG. 4 is a block diagram showing a configuration of a conventional key telephone system adapted to U point of an ISDN line.
A key telephone system 50 includes an ISDN interface unit (I/F unit) 51 for connecting with an ISDN network 60 and an ISDN terminal 70, and a control unit 52 for controlling the ISDN interface unit 51 and executing the calling process and the speech exchange process.
The ISDN interface unit 51 and the control unit 52 exchange various signals such as speech data, a clock signal, a frame synchronization signal, a control signal, etc. via an internal bus 53.
FIG. 5 is a block diagram showing the structures of the ISDN interface unit 51 and the control unit 52.
The ISDN interface unit 51 includes an interface LSI 80 for interfacing (called NT) with the ISDN network 60, and an interface LSI 81 for interfacing (called LT) with the ISDN terminal 70. The interface LSI 80 is fixed to the NT mode that allows the operation to be made in accordance with a clock signal extracted from the ISDN network 60. The interface LSI 81 is fixed to the LT mode that makes the terminal synchronous by using its own clock signal. A port corresponding to the NT mode is called a line port and a port corresponding to the LT mode is called an extension port.
When the interface LSI 80 is set to extract clock signal CLK from the ISDN network 60, i.e. when the interface LSI 80 is set in the NT mode, a switch unit 82 is turned on and a switch unit 84 is turned off. The interface LSI 80 extracts the clock signal CLK from the ISDN network 60 and outputs the signal through its own clock port.
The clock signal CLK that is output from the interface LSI 80 is input to a timing generation unit 85 of the control unit 52 as basic clock signal CLKb through the switch unit 82.
The timing generation unit 85 generates system clock signal CLKs in accordance with the basic clock signal CLKb and supplies this signal to both a time switch unit 86 of the control unit 52 and a phase adjustment time switch unit 83 of the ISDN interface unit 51 to make synchronization in the system. The timing generation unit 85 also generates a frame synchronization signal FS and outputs the signal to the phase adjustment time switch unit 83 and the time switch unit 86.
Synchronization between the interface LSI 80 and the interface LSI 81 is made by the clock signal CLK that is output from the interface LSI 80 and the frame synchronization signal FS. The speech data of the interface LSI 80 and the interface LSI 81 is transmitted to the phase adjustment time switch unit 83 in a single speech data highway DH1 and further transmitted to the time switch unit 86 in a speech data highway DH2 synchronized with the time switch unit 86.
When the interface LSI 80 is set not to extract the clock signal CLK from the ISDN network 60, i.e. when the interface LSI 80 is set in the LT mode, the switch unit 82 is turned off and the switch unit 84 is turned on. The interface LSI 80 and the interface LSI 81 are made synchronized with the system by the system clock signal CLKs and the frame synchronization signal FS that are generated by the timing generation unit 85 of the control unit 52. At this time, the clock ports of the interfaces LSIs 80 and 81 are set in the input state.
In the case of the conventional key telephone system constituted as described above, the interface LSIS 80 and 81 are fixed to either the NT mode or the LT mode and, therefore, the degree of freedom in the selection of the line is small. For example, if the user requires two interfaces in the NT mode, it is necessary to prepare for another ISDN interface unit 51. For this reason, the circuitry of the system becomes larger and the miniaturization is prevented, and the manufacturing costs are increased.
FIG. 6 is a block diagram showing the configurations of an ISDN interface unit 56 and a control unit 57 in the conventional key telephone system adapted to S and T points of the ISDN line.
The ISDN interface unit 56 includes an interface LSI 120 for interfacing (called TE) with the ISDN network 60 and an interface LSI 121 for interfacing (called NT) with the ISDN terminal 70. The interface LSIs 120 and 121 are fixed to either the TE or the NT.
When the interface LSI 120 is set to extract the clock signal CLK from the ISDN network 60, i.e. when the interface LSI 120 is set in the TE, the interface LSI 120 extracts the clock signal CLK from the ISDN network 60 and outputs the signal through the clock port. The clock signal CLK output from the interface LSI 120 is input to a timing generation unit 123 of the control unit 57.
The timing generation unit 123 generates the system clock signal CLKs in accordance with the clock signal CLK and supplies the signal to the interface LSI 121 that synchronizes with the timing generation unit 123 as a slave at the NT mode. The timing generation unit 123 also generates a frame synchronization signal FS1. The frame synchronization signal FS1 is supplied to a phase adjustment time switch unit 122 together with a frame synchronization signal FS2 output from the interface CSI 120. Speech data DS1 and DS2 of the interface LSIs 120 and 121 is supplied from the phase adjustment time switch unit 122 to the a time switch unit 124 of the control unit 57 in a single speech highway HS.
In the interface LSI 121, the frame synchronization is executed by using the frame synchronization signal FS1 generated by the timing generation unit 123 of the control unit 57, due to the slave-synchronization.
In the case of this conventional key telephone system, like the above-described key telephone system, the interface LSIs 120 and 121 are fixed to either the NT mode or the TE mode and, therefore, the degree of freedom in the selection of the line is small. If the user requires two NT functions, it is necessary to prepare for another ISDN interface unit 56. For this reason, the circuitry of the system becomes larger and the miniaturization is prevented, and the manufacturing costs are increased.
The present invention is accomplished in consideration of such circumstances, and the object thereof is to provide an electronic exchange capable of certainly making forwarding to a telephone at the forwarding destination and a key telephone system with a high degree of freedom in the selection of the line.
To achieve the object, according to the first aspect of the present invention, an electronic exchange capable of controlling call reception from and call transmission to other electronic exchanges is provided. The electronic exchange comprises means for receiving a request for a forwarding from the other electronic exchanges, and prohibiting means for setting a telephone of forwarding destination connected to the own electronic exchange to be in a state of prohibiting the call reception except for the forwarding or the call transmission at the time to make the telephone shift to a standby state for the forwarding in response to the request for the forwarding.
According to the present invention, the telephone of the forwarding destination is shifted from the idle state to the receiving standby state for the forwarding, in response to the request for forwarding from the other electronic exchange, so as to set the call transmission and the call reception except for the forwarding at the telephone to be impossible.
Therefore, even if calling operations are executed at the telephone of the forwarding destination or there is a call from a different telephone, the calling is invalid and thereby the forwarding of the call can be certainly accomplished. Further, the data traffic is not unnecessarily increased since an invalid signal is not transmitted into the network as seen in the prior art
It is p referable that the electronic exchange is capable of controlling th e call reception from and call transmission to the other electronic exchanges under the QSIG protocol.
It is preferable that when the telephone of forwarding destination connected to the own electronic exchange is idle after receiving a request for the forwarding, the telephone is made to shift to be in a standby state for the forwarding.
It is preferable that the electronic exchange further comprises announcement setting means for setting the telephone so as to announce to a user of the telephone that the telephone is set in the prohibition state.
According to the present invention, it is announced to the user of the telephone that the call reception except for the forwarding and the call transmission are prohibited.
Thus, t he user of the telephone at the forwarding destination can recognize that the forwarding is to be made. Therefore, he can properly make further response without being confused or making a mistake in the operations.
The announcement setting means may set the telephone so as to operate a sound source provided in the telephone, set the telephone so as to display predetermined information on a display unit provided on the telephone, or set the telephone so as to turn on a light of a display unit provided on the telephone.
In addition, the announcement setting means may set the telephone so as to operate a sound source provided in the telephone when a calling key of the telephone is pushed down in a period from the time of shifting to the standby state for the forwarding to the time of receiving an incoming of call caused by the forwarding. The announcement setting means sets the telephone so as to display predetermined information on a display unit provided on the telephone when a calling key of the telephone is pushed down in the period from the time of shifting to the standby state for the forwarding to the time of receiving an incoming of call caused by the forwarding.
Further, the announcement setting means may set the telephone so as to turn on a light of a display unit provided on the telephone when a calling key of the telephone is pushed down in the period from the time of shifting to the standby state for the forwarding to the time of receiving an incoming of call caused by the forwarding. The announcement setting means may also set the telephone so as not to accept input made by a dial key when a calling key of the telephone is pushed down in the period from the time of shifting to the standby state for the forwarding to the time of receiving an incoming of call caused by the forwarding.
According to another aspect of the present invention, an electronic exchange capable of controlling call reception from and call transmission to other electronic exchanges is provided. The electronic exchange comprises means for receiving a request for a forwarding from the other electronic exchanges, and announcement setting means for setting a telephone of forwarding destination connected to the own electronic exchange to announce to a user of the telephone that the telephone is set in a standby state for the forwarding at the time to make the telephone shift to the standby state for the forwarding in response to the request for the forwarding.
According to the present invention, it is announced to the user of the telephone in response to the request for forwarding that the forwarding destination is in the incoming standby state. The user of the telephone at the forwarding destination can thereby recognize that the forwarding is to be made and, therefore, he can properly make further response without being confused or making a mistake in the operations.
According to the other aspect of the present invention, an electronic exchange for connecting calling from a telephone connected to other electronic exchange to an outside line connected to the own electronic exchange, under the QSIG protocol that is an international standard of digital lines. The electric exchange comprises means for receiving information to restrict the calling from the other electronic exchange at the time of the calling from the telephone; and means for restricting the calling from the telephone to the outside line in response to the calling restriction information. The calling restriction information is added to a caller number notification information element of the QSIG protocol.
According to the present invention, the calling restriction information can be transmitted technically easily at low costs without using a specific information element, by adding the calling restriction information to the caller number notification information element of the QSIG protocol.
It is preferable that the electronic exchange further comprises a table for storing calling restriction contents and the calling restricting means searches for the calling restriction contents on the table in response to the calling restriction information and restricts the calling in accordance with the searched calling restriction contents.
According to the other aspect of the present invention, a key telephone system is provided. The key telephone system comprises interface means having a line interface function of transmitting digital data to an ISDN network via a U point of an ISDN line and an extension interface function of transmitting digital data to an ISDN terminal, for selectively setting one of the functions; and control means for setting the interface means to implement one of the line interface function and the extension interface function in accordance with line setting information.
According to the present invention, one interface means can be freely set to implement the line interface function or the extension interface function.
Therefore, it is possible to implement a key telephone system with a high degree of freedom, in which the number of the ISDN line ports and that of extension ports can be increased or decreased in accordance with the application.
According to the other aspect of the present invention, a key telephone system is provided. The key telephone system comprises interface means having a line interface function of transmitting digital data to an ISDN network via a U point of an ISDN line and an extension interface function of transmitting digital data to an ISDN terminal, for selectively setting one of the functions; timing generating means for generating a system clock signal and a frame synchronization signal in accordance with a clock signal output from the interface means when the interface means is set to implement the line interface function, and for generating the system clock signal and the frame synchronization signal in accordance with an internal clock signal when the interface means is set to implement the extension interface function; first switch means interposed into a signal transmission path between a clock signal input/output terminal of the interface means and a clock signal input/output terminal of the timing generating means; second switch means interposed into a signal transmission path between a system clock signal output terminal and a frame synchronization signal output terminal of the timing generating means, and a clock signal input/output terminal and a frame synchronization signal input/output terminal of the interface means; and control means for setting the interface means to implement one of the line interface function and the extension interface function in accordance with line setting information, for turning on the first switch means and turning off the second switch means when the interface means is set to implement the line interface function, and for turning off the first switch means and turning on the second switch means when the interface means is set to implement the extension interface function.
According to the present invention at the U point of the ISDN line, the line interface function and the extension interface function of the interface means are set by the control means. When the interface means is set to implement the extension interface function, the first switch means is turned off and the second switch means is turned on by the control means to use the internal clock signal of the timing generating means. The control means sets the line interface function and the extension interface function of the interface means in accordance with the line setting information.
Thus, the interface means can be freely set to implement either the line interface function or the extension interface function.
Therefore, it is possible to implement a key telephone system with a high degree of freedom, in which the number of the ISDN line ports and that of extension ports can be preferably increased or decreased.
According to the other aspect of the present invention, a key telephone system is provided. The key telephone system comprises interface means having a line interface function of transmitting digital data to an ISDN network via S and T points of an ISDN line and an extension interface function of transmitting digital data to an ISDN terminal, for selectively setting one of the functions; first switch means connected to the interface means, for changing a transmission line and a reception line respectively at the time of setting the line interface function and at the time of setting the extension interface function; second switch means interposed into signal transmission paths of a clock signal and a frame synchronization signal to the interface means, for changing input/output of the clock signal and the frame synchronization signal to the interface means; and control means for setting the interface means to implement one of the line interface function and the extension interface function in accordance with the line setting information, for changing the second switch means to the side of outputting the clock signal and the frame synchronization signal when the interface means is set to implement the line interface function, and for changing the second switch means to the side of inputting the clock signal and the frame synchronization signal when the interface means is set to implement the extension interface function.
According to the present invention, the first switch means for reversing the transmission line and the reception line is provided in front of the interface means so that the transmission line and the reception line are changed at the S and T points of the ISDN line. The control means also sets to implement the line interface function and the extension interface function of the interface means, and controls the changing of the second switch means.
When the first switch means is changed to the line interface function side, the line setting information to be set to implement the line interface function is input to the control means. On the other hand, when the second switch means is changed to the extension interface function side, the line setting information to be set to implement the extension interface function is input to the control means.
After inputting the line setting information to be set at the line interface function, the control means sets the interface means to implement the line interface function and changes the second switch means to the side of outputting the clock signal and the frame synchronization signal.
When the control means is input the line setting information to be set at the extension interface function, the control means sets the interface means to implement the extension interface function and changes the second switch means to the side of inputting the clock signal and the frame synchronization signal.
Therefore, the interface means can be freely set to implement either the line interface function or the extension interface function. For this reason, a key telephone system with a high degree of freedom can be provided.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.